<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>input占位文本</title>
</head>
<body>
  文本框：<input type="text" placeholder="请输入用户名">
  <br><br>
  密码框：<input type="password" placeholder="请输入密码">
</body>
</html>